Method for control regenerative braking of electric vehicle

ABSTRACT

A method for controlling regenerative braking of a vehicle includes initiating the regenerative braking, detecting an amount of slip of a wheel during the regenerative braking, if the amount of slip is increasing, reducing a regenerative braking torque, and if the amount of slip is greater than a set value, actuating an antilock brake system and reducing the regenerative braking torque or a hydraulic braking torque continuously until the vehicle is stopped. Alternatively, if the amount of slip is increasing, the regenerative braking torque is not reduced.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 11/648,765 filed Dec. 29, 2006, which claimspriority to Korean Patent Application Nos. 10-2006-0104302 and10-2006-0104304, both filed on Oct. 26, 2006, in the Korean IntellectualProperty Office, the entire content of which applications isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for controlling regenerativebraking of an electric vehicle, and more particularly to a method forcontrolling regenerative braking of an electric vehicle that reducesregenerated braking torque gradually.

2. Description of the Related Art

Generally, an electric vehicle uses regenerative braking. Sometimessufficient braking can not be obtained with only regenerative braking.An electric vehicle thus also contains a hydraulic brake system toelicit braking force by oil pressure

US patent published No. 2002/018266 discloses a braking force controlsystem in the beginning of ABS control during regenerative braking. Theregenerative braking torque is decreased progressively and when ABScontrol has begun, the regenerative braking is turned off, then thenecessary braking torque is controlled by hydraulic pressure.

During regenerative braking, when reducing the regenerative brakingtorque before beginning the ABS activation, energy recovery isdecreased. Furthermore, when the regenerative braking is turned off, theactual braking force is lower than the goal braking force.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present invention provides a method for controlling regenerativebraking of an electric vehicle. During the regenerative braking, theregenerative braking torque is reduced progressively before and duringABS control.

An exemplary method for controlling regenerative braking includesbeginning regenerative braking, detecting an amount of slip of a frontwheel, reducing the regenerative braking torque if the amount of slip isincreasing before an ABS is actuated, and continuing to reduce theregenerative braking torque during the ABS actuating if the amount ofslip is larger than a standard value.

If regenerative braking torque is insufficient during the ABSactivation, hydraulic torque may be used.

Further, after actuating the ABS, if the necessary reduction amount ofbraking torque is more than the reduction amount of the regenerativebraking torque, the hydraulic braking torque is decreased.

An alternative method includes: beginning regenerative braking of theelectric vehicle, detecting a front wheel slip amount during theregenerative braking, if the front wheel slip amount is above a standardvalue, actuating the ABS and continuously decreasing the regenerativebraking torque until the vehicle is stopped, and if the front wheel slipamount is increasing before actuating the ABS, not decreasing theregenerative braking amount.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will become apparent and morereadily appreciated from the following description of the preferredembodiments, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a method for controlling regenerative brakingaccording to a first exemplary embodiment of the present invention.

FIG. 2 illustrates a method for controlling regenerative brakingaccording to a second exemplary embodiment of the present invention.

FIG. 3 illustrates a method for controlling regenerative brakingaccording to a third exemplary embodiment of the present invention.

FIG. 4 is a flowchart illustrating a method for controlling regenerativebraking according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method for controlling regenerativebraking according to the second and third embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method for controlling regenerative braking of electricvehicle according to embodiments of the present invention will bedescribed with reference to the drawings.

Referring to FIGS. 1 and 4, in a first exemplary embodiment, the presentinvention controls regenerative braking torque at the beginning of ABScontrol, to promote energy recovery while reducing the regenerativebraking torque gradually if the slip amount of a wheel is increasingbefore the initiation of ABS actuating.

The regenerative braking torque is reduced until the vehicle stopsduring ABS actuating if the slip amount of a front wheel is larger thana standard value, improving the feeling of braking and energy recovery.

Hydraulic braking is also used during the ABS actuating.

Referring to FIGS. 2 and 5, in a second embodiment, if the slip amountis increased before actuating the ABS, the actuating signal istransferred to the motor by the controller of the regenerative brakingand the regenerative braking torque is not reduced.

Here, if the amount of front wheel slip is larger than the standardvalue, at the same time of initiating the ABS actuating, theregenerative braking torque is reduced until vehicle stop.

Meanwhile, the hydraulic braking torque is reduced when the neededdecrement of braking torque is larger than the decrement of theregenerative braking torque.

Referring to FIG. 3, a third exemplary embodiment differs from thesecond embodiment in that the needed decrement of braking torque isprimarily reduced from the hydraulic braking torque, without reducingthe regenerative braking torque, and the regenerative braking torque isreduced when the needed decrement of braking torque is larger than thedecrement of hydraulic braking torque.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A method for controlling regenerative braking of a vehicle,comprising: initiating the regenerative braking; detecting an amount ofslip of a wheel during the regenerative braking; if the amount of slipis increasing, reducing a regenerative braking torque; and if the amountof slip is greater than a set value, actuating an antilock brake systemand reducing the regenerative braking torque continuously until thevehicle is stopped.
 2. The method of claim 1, wherein a hydraulic torqueis used if the regenerative braking torque is insufficient.
 3. Themethod of claim 2, wherein the hydraulic braking torque is reduced if aneeded reducing amount of braking torque is larger than a reducingamount of the regenerative braking torque.
 4. A method for controllingregenerative braking of a vehicle, comprising: initiating theregenerative braking; detecting an amount of slip of a wheel during theregenerative braking; if the amount of slip is increasing, not reducinga regenerative braking torque; and if the amount of slip is greater thana set value, actuating an antilock brake system and reducing theregenerative braking torque continuously until the vehicle is stopped.5. A method for controlling regenerative braking of a vehicle,comprising: initiating the regenerative braking; detecting an amount ofslip of a wheel during the regenerative braking; if the amount of slipis increasing, not reducing a regenerative braking torque; and if theamount of slip is greater than a set value, actuating an antilock brakesystem and reducing a hydraulic braking torque continuously until thevehicle is stopped.
 6. The method of claim 5, wherein the regenerativebraking torque is reduced if a needed reducing amount of braking torqueis larger than a reducing amount of the hydraulic braking torque.